1. Field of the Invention
This invention relates to processing of video signals, and more specifically to correction of light intensities output by the screen of a computer display monitor.
2. Description of the Prior Art
Display monitors (such as used in computer systems) tend to output varying amounts of light as a function of position on the monitor CRT (cathode ray tube) screen for a given pixel value (level of light intensity). Monitor screen light output also tends to vary in "color temperature" from unit to unit. Color temperature is a well known measure of intensity which typically is a function of the mix of colors which make up white light. These deficiencies cause inaccurate and inconsistent representations of graphics images on the monitor.
Some prior art CRT's used in monitors are manufactured to compensate for the undesirable tendency of CRT's to be bright in the center and less intense on the edges; the result typically is to provide somewhat lessened intensity variation; however, an undesirable "target" pattern in color intensity which is not 100% uniform is still present. Also, not all monitors have this built-in compensation.
This variation in color intensity is especially problematic when the monitor is used as part of a computer system for editing and processing of color images, such as in the printing industry. In this case, the variations in light intensity tend to cause undesirable color variations in the displayed image versus the intended image, which is typically a photographic image with true colors.